As long as life existed, recycling was the way to balance the life cycle on this planet. We currently have the technology to recycle most of our waste, but most recycling technologies are not profitable and are therefore not likely to be implemented. In particular, the large scale processing and recycling of animal, bird and human feces, which is generated in enormous amounts on huge industrialized bird and animal farms, and in our own cities, is extremely problematic.
For hundreds of millions of years, flies have been depositing their larvae onto animal feces and in the process of feeding, the larvae where transforming the feces into the best natural, organic fertilizer known and larvae them self, become the protein-rich food for birds and animals.
Beside some laboratory and pilot-plant experiments, there are a few known attempts to design equipment and plant layout, which would use larvae of flies to process animal and bird feces. The attempts where somewhat successful in obtaining organic fertilizers and protein rich mass of larvae, but this technology was not used much because of sever technological problems encountered during production and due to a lack of profitability of the plants. A few different systems have been tested in this field. In one system, flies are simply allowed to deposit larvae on the pile of feces placed in a pit and mature larvae were collected as they try to migrate out of the pile, to start the process of pupating. Only a portion of feces close to the surface where transformed to the fertilizer and the rest of feces simply degraded anaerobic, releasing large amounts of ammonia, formaldehyde and other highly polluting green house gasses into the atmosphere. A huge infestation of flies tormented the neighborhoods and leakage from the pile polluted soil and water.
In an other system, feces (“substrate”) is deposited directly onto a conveyer belt, seeded with larvae of flies and the conveyer itself is used as a reaction vessel. In another system, trays with substrate piled there on are seeded with fly larvae and are moved on conveyer belts through the process for several days, until the substrate was transformed into the organic fertilizer.
Attempts to use conveyer belts as a reaction vessel created many difficulties. One of the difficulties is that older larvae would migrate into the territory of younger larvae and compete with the younger larvae for the food, causing a food shortage for younger larvae, which would stay underdeveloped. On the other side, where older larvae migrated from, the substrate is left with not enough larvae to finish the process, so some substrate remained unprocessed. Also, a thick crust of dried out substrate, formed on the top of the processed material, could not be processed by larvae. The thick crust also prevents poisonous decomposition gasses from leaving the substrate. Removing the crust with scrapers is a very messy and costly procedure.
Also, conveyer belt systems, as used now, are very bulky, very messy, and require huge facilities but offers very low productivity (capacity per occupied area). The high cost of energy makes it very costly to maintain large facilities, especially in this industry, where the cost of heating and ventilation makes up a large portion of operating expenses.
Some improvements are made by placing 3 conveyer belts one on top other and using each level as a reaction vessel for one-day production. In such a system, two sets of 3 conveyers are used to finish the process of conversion. These triple conveyer systems solved the problem of older larvae migrating to the substrate of younger larvae, because in these triple conveyer systems all the larvae on one level are of the same age.
Using triple conveyer systems created new problems. Within the triple conveyer system, as they are now, heating and ventilation problems where solved by placing the conveyers within the long tunnels and blowing warm air along the tunnels. If the air flow along the tunnel is slow, the end of the tunnel never gets sufficient ventilation but if the air speed along the tunnel is too fast, the substrate at the beginning of the tunnel gets very dry and larvae could not process it. To decrease the speed of air and get sufficient air flow at the same time, the size of the tunnel had to be enlarged to the height of 60 cm to 70 cm, making it very messy and difficult to contain and control the substrate when dropping from that height and at the same time making the whole system very bulky and inefficient. The length of the tunnel should normally increase the capacity and efficiency of the system, but the longer the tunnel gets, the higher it has to be to obtain the proper ventilation, which unfortunately increases bulkiness and decreases efficiency. Ventilation along the tunnel was definitely problematic.
The moving tray system is similar to the conveyer belt system but instead of loading the substrate directly onto a conveyer belt, the substrate is loaded into a plurality of trays and the trays are placed onto the conveyer belt creating similar ventilation problems. In a tray based system, older larvae could not migrate to the trays with younger larvae but they also could not get out of the substrate after the process is finished. Also, this design does not lend itself to a multi-layer or stacked design, so the process is much bulkier and less productive.
Static trays have also been suggested for use with this technology. Unfortunately, filling, emptying, cleaning and handling large amounts of trays is very difficult and costly, for any system using trays. Furthermore, the ventilation and formation of dry crust where not solved in any of the tray systems as well. As a result of everything, tray systems, as they are now, are very costly, and problematic, acceptable only for small laboratory operations.
None of the above processes utilizes an efficient and economical solution for heating and ventilation of processing facilities, which represent a good portion of operating expenses.
Preheating of substrate was also not solved efficiently in any of the prior existing processes, resulting in more degradation and more decomposition products, requiring additional ventilation during the processing. The prior art calls for preheating of the substrate within the receiving tank, which is acceptable for the smaller quantities, but not so practical in case of larger tanks and larger quantities of substrate. Small quantity of substrate could be preheated in a few hours with the use of heaters placed on the outside surfaces of a smaller substrate receiving tank, but for a larger amount of substrate in colder climates, heating within the receiving tank, from the outside of the tank, could take days to reach the suitable working temperature. High temperatures could not be used to speed up the heating within the large tanks, because mixing in large tanks could never be good enough to prevent drying or burning of substrate on the heated surfaces. The gasses from burned substrate would require even more ventilation.
Preheating the entire substrate within the larger tanks also increases the speed of decomposition of the entire mass of substrate producing much more decomposition gasses what would again require more vigorous ventilation during the processing. Also, mixing the old substrate with the fresh one would increase the decomposition of the fresh substrate by introducing a decay causing bacteria from the old substrate. Preheated and seeded with decay-causing bacteria, the entire mass of substrate would decay rapidly releasing ammonia, formaldehyde and other poisonous gasses, again requiring additional and more vigorous ventilation during the processing.
Given the numerous drawbacks of the prior art systems of substrate processing, improved systems are desirable. The improved system would overcome the problems of low productivity, poor and expensive heating & ventilation, mixing and preheating of entire substrate within the tank and others. All of the improvements would lead to sufficient profitability and thus, acceptance of this technology by the industry.